12.16.7.1 General Geometry Property Functions

The functions listed in this section do not restrict their argument and accept a geometry value of any type.

• Dimension(g)

  ST_Dimension() and Dimension() are synonyms. For more information, see the description of ST_Dimension().

• Envelope(g)

  ST_Envelope() and Envelope() are synonyms. For more information, see the description of ST_Envelope().

• GeometryType(g)

  ST_GeometryType() and GeometryType() are synonyms. For more information, see the description of ST_GeometryType().

• IsEmpty(g)

  ST_IsEmpty() and IsEmpty() are synonyms. For more information, see the description of ST_IsEmpty().

• IsSimple(g)

  ST_IsSimple() and IsSimple() are synonyms. For more information, see the description of ST_IsSimple().

• SRID(g)

  ST_SRID() and SRID() are synonyms. For more information, see the description of ST_SRID().

• ST_Dimension(g)

  Returns the inherent dimension of the geometry value g, or NULL if the argument is NULL. The dimension can be −1, 0, 1, or 2. The meaning of these values is given in Section 11.4.2.2, “Geometry Class”.

  mysql> SELECT ST_Dimension(ST_GeomFromText('LineString(1 1,2 2)'));
  +------------------------------------------------------+
  | ST_Dimension(ST_GeomFromText('LineString(1 1,2 2)')) |
  +------------------------------------------------------+
  |                                                    1 |
  +------------------------------------------------------+

  ST_Dimension() and Dimension() are synonyms.

• ST_Envelope(g)

  Returns the minimum bounding rectangle (MBR) for the geometry value g, or NULL if the argument is NULL. The result is returned as a Polygon value that is defined by the corner points of the bounding box:

  POLYGON((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY))

  mysql> SELECT ST_AsText(ST_Envelope(ST_GeomFromText('LineString(1 1,2 2)')));
  +----------------------------------------------------------------+
  | ST_AsText(ST_Envelope(ST_GeomFromText('LineString(1 1,2 2)'))) |
  +----------------------------------------------------------------+
  | POLYGON((1 1,2 1,2 2,1 2,1 1))                                 |
  +----------------------------------------------------------------+

  ST_Envelope() and Envelope() are synonyms.

• ST_GeometryType(g)

  Returns a binary string indicating the name of the geometry type of which the geometry instance g is a member, or NULL if the argument is NULL. The name corresponds to one of the instantiable Geometry subclasses.

  mysql> SELECT ST_GeometryType(ST_GeomFromText('POINT(1 1)'));
  +------------------------------------------------+
  | ST_GeometryType(ST_GeomFromText('POINT(1 1)')) |
  +------------------------------------------------+
  | POINT                                          |
  +------------------------------------------------+

  ST_GeometryType() and GeometryType() are synonyms.

• ST_IsEmpty(g)

  This function is a placeholder that returns 0 for any valid geometry value, 1 for any invalid geometry value, or NULL if the argument is NULL.

  MySQL does not support GIS EMPTY values such as POINT EMPTY.

  ST_IsEmpty() and IsEmpty() are synonyms.

• ST_IsSimple(g)

  Returns 1 if the geometry value g has no anomalous geometric points, such as self-intersection or self-tangency. ST_IsSimple() returns 0 if the argument is not simple, and NULL if the argument is NULL.

  The descriptions of the instantiable geometric classes given under Section 11.4.2, “The OpenGIS Geometry Model” includes the specific conditions that cause class instances to be classified as not simple.

  ST_IsSimple() and IsSimple() are synonyms.

• ST_SRID(g)

  Returns an integer indicating the spatial reference system ID associated with the geometry value g, or NULL if the argument is NULL.

  mysql> SELECT ST_SRID(ST_GeomFromText('LineString(1 1,2 2)',101));
  +-----------------------------------------------------+
  | ST_SRID(ST_GeomFromText('LineString(1 1,2 2)',101)) |
  +-----------------------------------------------------+
  |                                                 101 |
  +-----------------------------------------------------+

  ST_SRID() and SRID() are synonyms.